ICAO set to issue revised WAAS approach criteria

The International Civil Aviation Organization (ICAO) announced it will issue revised standards for helicopter navigation this fall that are intended to take advantage of GPS receiver technology and new types of instrument approach procedures.

The first set of standards will deal with vertical and lateral guidance using the wide area augmentation system (WAAS) or its European equivalent, the European geostationary navigation overlay system (EGNOS)–both based on GPS augmentation. Another standard will cover simultaneous, parallel, non-interfering approaches at airports. Still in the rulemaking phase are point-in-space (PIS) approach standards and performance-based navigation for helicopters.

“In November ICAO will set international standards for using satellite-based augmentation systems for vertical and lateral guidance,” Yves Coutier, a French expert on ICAO’s obstacle clearance panel (OCP), told HAI Convention News. The panel is designing more suitable IFR procedures for helicopters by taking advantage of new navigation equipment. In the upcoming rules, precision approach angles up to approximately six degrees will be addressed. According to Coutier, there was no consensus to address steep angles above six degrees. One reason was the high cost of the equipment needed to design such approaches.

Flight tests last year at Toulouse Airport in France helped to validate non-interfering approach criteria that will be included in the new rules. Eurocopter used an EC 155 Dauphin for various approach types. The medium-twin helicopter flew precision approach glideslopes as steep as nine degrees, thanks to a sophisticated autopilot. EGNOS augmentation of GPS signals provided almost the equivalent of a Category I ILS without the need for any ground equipment, Eurocopter’s research manager for operations Philippe Rollet told HAI Convention News. Rules for such non-interfering approaches go into effect in the fall, he said.

The PIS concept has been recognized by ICAO as appropriate for helicopter operations. The idea is to design an IFR route that ends at a relevant point, close to a heliport. The crew then flies VFR to the landing spot. Where a direct IFR approach is not feasible because of obstacles, points in space can significantly improve safety.

The simpler of two PIS options includes a direct final visual segment, standards for which will be published in November. The second option involves a less straightforward final segment. Still in discussion is the case where the PIS is not aligned with the final approach path and the pilot has to perform maneuvers. “We are trying to find ways to give better obstacle information to the crew,” Coutier explained. For example, standards are being defined to determine which obstacles should be equipped with lights.

Another evolution that ICAO experts are studying is moving from area navigation (Rnav) to performance-based navigation (PRnav). The idea is to require a level of navigation performance as opposed to specific equipment requirements. For example, “To fly approaches with vertical guidance designed according to barometric vertical navigation criteria, helicopters would no longer be required to have a flight management system on board, as long as they have an EGNOS or WAAS receiver,” Coutier said.

Heliport Layout Rules Changing, Too

On November 20 new ICAO rules governing heliport layout will go into effect. They will cover construction, obstacle limitation or suppression, marking and lighting. Affected will be land heliports, offshore helidecks and shipboard helipads. However, many of the changes will apply to shipboard helipads and offshore helidecks that are completed after Jan. 1, 2012. Members of ICAO’s Heliport Design Working Group anticipate further modifications to heliport standards, but not until 2010.